This invention relates to an improved apparatus for forcibly bringing the air and water into contact together, and more specificially to an improved cooling apparatus such as cooling tower or evaporative condenser.
In general, when water sprayed into the air and fell onto a water vessel is pumped and is sprayed again repetitively, the temperature of water gradually approaches the wet bulb temperature of the air. Widely known cooling apparatus utilizing this principle may be represented by cooling towers or evaporative condensers. As is well known, according to such apparatus, the air stream is forcedly created in the tower by a fan in order to increase the contacting amount between water and air; hence the cooling capacity of such apparatus varies in proportion to the difference in enthalpy between the air and the air of a temperature equal to the temperature of the water. The enthalpy of the air is approximately represented by the wet bulb temperature. Substantially, therefore, it is proper to say that the cooling ability or capacity is dependent upon the difference between the wet bulb temperature of the outdoor air and the temperature of the cooling water at the inlet port. Consequently, the change in the outdoor air wet bulb temperature or in the temperature of the cooling water naturally causes the cooling capacity of the cooling tower to be varied.
According to most of the conventional cooling apparatus of this type, however, the water feeding rate L (kg/hr) and the air feeding rate G (kg/hr) have been maintained constant. it is a generally accepted idea that a refrigerator operates with a reduced load when the outdoor atmospheric or air temperature is low and when the outdoor air wet bulb temperature is low. In such a case, the cooling tower having increased cooling ability should be operated at reduced cooling capacity. In spite of this fact, however, the conventional cooling towers have not been controlled to follow such changes in temperatures.
In particular, the cooling towers are often irrationally operated during the seasons of spring and fall; the temperature of the cooling water is often excessively lowered. In winter, the temperature of the cooling water may further decrease, making it difficult to control the refrigerating capacity of the refrigerator, or giving rise to the occurrence of a refrigerant backing phenomenon or increase in the consumption of the electric power, causing the apparatus to become inoperative or presenting damage to the compresser finally.
In order to overcome such disadvantages, U.S. Pat. No. 2,287,297 discloses fan blades of a fan which can be varied. The fan having such variable blades, however, is very expensive, and permits the blowing amount of the air to be varied only within a narrow range, and is therefore not practicable. Another system to cope with the above-mentioned defects is to control the amount of the water supplied to the tower by providing a cross or three-way valve and a by-pass conduit between the cooling water inlet port and the cooling water outlet port of the cooling tower. This system, as is well known, has now been extensively used. However, since the amount of the cooling water is made variable, it is difficult to maintain desired cooling performance and to keep the cooling water at an uniform dispersion in the tower. A further method to cope with the above-mentioned defects consists of automatically controlling the start and stop of the fan and a fan motor. According to this method, however, the electric motor is very frequently started and stopped especially in the winter season, thus giving a conflicting nature to the recent tendency toward saving the energy. Therefore, it has been urged to provide a fan which suits for the cooling apparatus such as cooling tower, which can be cheaply manufactured, and of which the running speed can be continuously and proportionally changed.